We are in the process of configuring our Inventory module and processed a Pick List and Delivery Order automatically created from a Sales Order.

The Sales Order exceeded the quantity of items in the nominated source location but there was no indication of this in either the Pick List or the Delivery Order - both were processed as normal and the Delivery Order was marked as completed. 

However afterwards, when we checked the source location, the remaining count of items was negative. How can this happen and how can I prevent it happening again? Thanks.